10 September 2015, The Conversation, Sure, winter felt chilly, but Australia is setting new heat records at 12 times the rate of cold ones. Spring feels like a welcome relief from an Australian winter that felt very cold and very long. Melbourne has just shivered through its coldest winter in 26 years and Canberra hibernated through more cold nights than any winter since 1997. But while it felt cold, it turns out we’ve just become accustomed to unusually warm conditions. My new study online in Geophysical Research Letters (with my colleague Andrew King) shows that Australia has been losing out on cold temperature records over the past 55 years. We investigated the frequency of new hot and cold temperature records for months, seasons and years, for each state and Australia as a whole, from 1910 to 2014. The results were straightforward. Record-breaking hot temperatures have outnumbered new cold records by a factor of 12 to 1 since the beginning of this century. The cause is also clear: global warming. Yet people’s ability to recognise climate extremes is easily affected by our perceptions. Riding my bike around frosty Canberra this winter felt brutally and unusually cold. But in reality it was only a bit colder than recent “warm” winters. Such misperceptions about climate extremes are common. During the record-breaking spring temperatures in Australia in 2013, Prime Minister Tony Abbott said: “…the thing is that at some point in the future, every record will be broken, but that doesn’t prove anything about climate change. It just proves that the longer the period of time, the more possibility of extreme events.” At first pass, this sounds like common sense. But statistically, it’s wrong. In an unchanging climate, new temperature records actually become less likely to occur with time, because each new record would be harder to beat in the absence of anything driving temperatures in a particular direction. Read More here
Category Archives: Impacts Observed & Projected
4 September 2015, Climate News Network, Global tree census highlights need to restore forests. Mapping the density of forests reveals that there are far more trees on the planet than previously thought – but humans are destroying 15 billion a year. An international collaboration of scientists has just completed the ultimate green census – by calculating that the planet is home to 3.04 trillion trees. The latest estimate is far higher and almost certainly more accurate than any previous attempt. But the bad news is that humans are removing trees at the rate of 15 billion a year – and there are now about half as many as there were at the dawn of civilisation. For every person on Earth, there are 422 trees – in total, more than 3,000 billion deciduous or evergreen growths with woody trunks greater than 10 centimetres at breast height. The researchers based their study on close analysis of satellite imagery, and of data from 429,775 plots of trees as measured on the ground in 50 countries on every continent except Antarctica. Statistical techniques. They counted forests in 14 “biomes” − or different kinds of climate, soil and topography − and in places not normally associated with trees, such as deserts, savannah, swamps, tundra and high mountains. They then they used statistical techniques that could extend their sample density measurements to the whole terrestrial world. The scientists report in Nature journal that the tropical and subtropical forests are home to 1.39 trillion trees, while the boreal forests of the north contain 0.74 trillion, and the temperate zones hold 0.61 trillion. Read More here
2 September 2015, Washington Post, Wildfires have now burned a massive 8 million acres across the U.S. As of Tuesday, according to the National Interagency Fire Center, more than 8 million acres have burned in U.S. wildfires in 2015. 8,202,557 of them, to be precise. That’s an area larger than the state of Maryland. And the numbers are still growing: 65 large fires are currently raging across the country, particularly in California, Oregon, Washington, Idaho and Montana. That includes three Washington state fires or fire complexes that are larger than 100,000 acres burned. As of this writing, the United States remains at wildfire preparedness level 5 — the highest level — where it has been since Aug. 13. There are only six other years that have seen more than 8 million acres burned — 2012, 2011, 2007, 2006, 2005, and 2004 — based on National Interagency Fire Center records that date back to 1960. It is hard not to notice that all of these years came since the year 2000. Read More here
29 August 2015, Climate News Network, Climate models may misjudge soils’ carbon emissions. How soil organisms cope with decaying vegetation is much less certain than climate models suppose, researchers say, and carbon emission estimates may be wrong. Some of the microscopic creatures which live in the soil are able to digest dead plants and trees, turning their contents into gas and minerals. But researchers say their work show that our understanding of how organic material is decomposed is fundamentally wrong, calling into question some current climate models. The researchers, from Lund University, Sweden, and the University of New Hampshire, USA, have published their study in the journal Ecological Monographs. They say it means that climate models which include micro-organisms in their estimates of future climate change must be reconsidered. When plants or trees die, their leaves and branches fall to the ground and the organic matter which is absorbed by the soil is then decomposed, mainly by the activity of fungi and bacteria, which convert the dead materials into the main greenhouse gas, carbon dioxide, and mineral nutrients. Until now, the Lund team says, scientists had thought that high-quality organic materials, such as leaves that are rich in soluble sugars, were mainly decomposed by bacteria, leaving the lower-quality matter, like cellulose and lignin, to be broken down mainly by fungi. Expectations confounded. Previous research has suggested that organic material decomposed by fungi results in less CO2 and nutrient leakage compared with matter decomposed by bacteria. This is important for the climate models in use today, as any change in the loss of CO2 and mineral nitrogen would alter the soil’s contribution to greenhouse gases and eutrophication, the process in which the release of excessive chemical pollution causes algal blooms in watercourses. Read More here